zfs discuss - Nov 2007 - Changing all the underlying device names...

Hi All,

I''m a new ZFS convert (so far, I''ve only been impressed by
ZFS) - I''m
running it under FreeBSD 7 atm.

I''ve got to ''shuffle'' all the underlying devices
around on my raidz pool -
so their device names will all either change (e.g. "da0" will become
"ad4")
- or the devices will get ''jumbled up'' (e.g. "ad16"
will become "ad22").

I''ve read bits and pieces about this - from what I''ve read, I
need to do a
''zpool export'' on the pool, shutdown the system - replace the
controllers -
run it all up, then do a ''zpool import''?

The man page mentions, a ''zpool import'' will search
''/dev/dsk'' or another
directory I give it - here''s hoping the FreeBSD port knows how to find
the
disks under /dev? :-)


Finally - if I do this and it all goes horribly wrong, presumably putting 
the old controllers back in place, with the drives in the
''right'' positions
- a ''zpool import'' will work?

Cheers,

-Kp

Hi Karl,

Karl Pielorz wrote:
> I''m a new ZFS convert (so far, I''ve only been impressed
by ZFS) - I''m
> running it under FreeBSD 7 atm.
> I''ve got to ''shuffle'' all the underlying devices
around on my raidz pool -
> so their device names will all either change (e.g. "da0" will
become "ad4")
> - or the devices will get ''jumbled up'' (e.g.
"ad16" will become "ad22").
> I''ve read bits and pieces about this - from what I''ve
read, I need to do a
> ''zpool export'' on the pool, shutdown the system - replace
the controllers -
> run it all up, then do a ''zpool import''?
Well .... you might need to do that on FreeBSD, I don''t know for
sure. On Solaris you wouldn''t need to do that because we use devids
(device ids) which help us to identify and track device movements.

You can read a bit more about it in my presentation

http://www.jmcp.homeunix.com/~jmcp/WhatIsAGuid.pdf

(and if you were in Brisbane, Australia tomorrow you could
  hear me deliver it in person @ HUMBUG http://www.humbug.org.au)

ahem. Shameless self-promotion ends :)

> The man page mentions, a ''zpool import'' will search
''/dev/dsk'' or another
> directory I give it - here''s hoping the FreeBSD port knows how to
find the
> disks under /dev? :-)
It should. I trust PJD''s implementation - as far as I''m aware
he''s got everything else right!
> Finally - if I do this and it all goes horribly wrong, presumably putting 
> the old controllers back in place, with the drives in the
''right'' positions
> - a ''zpool import'' will work?
I would hope so.


cheers,
James C. McPherson
--
Senior Kernel Software Engineer, Solaris
Sun Microsystems
http://blogs.sun.com/jmcp	http://www.jmcp.homeunix.com/blog

So we have a zpool that was grown over time by using the ''zpool
add''
command to add some space. This has ended up with a zpool made of three 
devices on our old hp san. This is on solaris 10 sparc.

I want to move the zpool to fc netapp storage using zpool replace, 
completely getting it off the HP. I can''t just replace the 3 devices 
with one big one, right? I''m thinking I''ll have to make 3
equivalently
sized luns on the netapp and "zpool replace" them individually. This 
ideally will happen with the zpool up and available.

Am I on the right track here?